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CZJ Flektogon 35mm f2.4 focusing distance scale misaligned?
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PostPosted: Tue Aug 04, 2020 10:00 am    Post subject: CZJ Flektogon 35mm f2.4 focusing distance scale misaligned? Reply with quote

Hello members.

I have a question about CZJ Flektogon 35mm f2.4 lens. The red stripe marking of focusing doesn't reach infinity focus mark on the distance scale. Was the lens disassembled earlier and assembled incorrectly where the helicoid was placed in a wrong position and now those distance scale marking are a bit off? I'm adding pictures to show the minimum and maximum I can reach while turning the focusing ring. I saw on other pictures and videos online of the same lens that the red stripe reaches the infinity marking on the distance scale, so I presume it is misaligned after assembling.

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PostPosted: Tue Aug 04, 2020 10:22 am    Post subject: Re: CZJ Flektogon 35mm f2.4 focusing distance scale misalign Reply with quote

aibo77 wrote:
Hello members.

I have a question about CZJ Flektogon 35mm f2.4 lens. The red stripe marking of focusing doesn't reach infinity focus mark on the distance scale. Was the lens disassembled earlier and assembled incorrectly where the helicoid was placed in a wrong position and now those distance scale marking are a bit off? I'm adding pictures to show the minimum and maximum I can reach while turning the focusing ring. I saw on other pictures and videos online of the same lens that the red stripe reaches the infinity marking on the distance scale, so I presume it is misaligned after assembling.

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PostPosted: Tue Aug 04, 2020 10:24 am    Post subject: Reply with quote

Yes, probably not skilled repair. (yes, if you reach infinity normally, otherwise there could be some obstruction in helicoid). This can be easily corrected disassembling from front side.


PostPosted: Tue Aug 04, 2020 12:34 pm    Post subject: Reply with quote

Pancolart wrote:
Yes, probably not skilled repair. (yes, if you reach infinity normally, otherwise there could be some obstruction in helicoid). This can be easily corrected disassembling from front side.


is it easy to disassemble and align the focusing distance scale to properly correspond to the range and movement of the focusing ring, or is it easy to remove an obstruction if there is something? I've watched a video on youtube of Flektogon disassemble and I have mixed feelings of easy/hard evaluation Very Happy If I don't touch the aperture mechanism, just go straight for the helicoid, mark the initial spot of how it aligns (to not make it worse if I can't do it better), maybe I can tweak it to be perfectly aligned by trial and error. If there would be some more info on internet about the helicoid part, that would be great, because that video is more concentrated to the cleaning of aperture blades and the helicoid assembling part goes through very fast.


PostPosted: Tue Aug 04, 2020 2:06 pm    Post subject: Reply with quote

Welcome aibo77!

I think during re-assembly the helicals were incorrectly aligned -- helical threads have more than one start point -- looks like if helicals were again separated, then re-started on the adjacent set of threads, the markings will align.


PostPosted: Tue Aug 04, 2020 2:29 pm    Post subject: Reply with quote

First you should sheck if just the focusing ring is misaligned or the whole lens.
Does it focus to infinity when fully retracted and to 0.2m when fully expanded? If yes, then it's just the focusing ring.


PostPosted: Tue Aug 04, 2020 3:18 pm    Post subject: Reply with quote

Alex TG wrote:
First you should sheck if just the focusing ring is misaligned or the whole lens.
Does it focus to infinity when fully retracted and to 0.2m when fully expanded? If yes, then it's just the focusing ring.


Yes it focuses through the whole range, it's just the markings that don't align to the red stripe, too much space in front of 0.2 mark and doesn't go till infinity mark.


PostPosted: Thu Aug 06, 2020 2:11 pm    Post subject: Reply with quote

The focusing system uses TWO helicoids, one with a multi-start coarse thread and another with a single-start fine thread. Probably the fine thread helicoid is one turn off. If this is the case, to fix it you need to loosen the stop screw and rotate the fine thread ring by one turn.


PostPosted: Thu Aug 06, 2020 3:08 pm    Post subject: Reply with quote

Gerald wrote:
The focusing system uses TWO helicoids, one with a multi-start coarse thread and another with a single-start fine thread. Probably the fine thread helicoid is one turn off. If this is the case, to fix it you need to loosen the stop screw and rotate the fine thread ring by one turn.


How do I get to that stop screw without disassembling the whole lens? Should I start from the front? "By one turn" do you mean full 360 degree turn around?


PostPosted: Thu Aug 06, 2020 4:05 pm    Post subject: Reply with quote

Yes, I meant one full turn (360 degree), but I am afraid you'll have to disassembly the focusing system, what isn't too difficult to do, but but it is a task that shouldn't be attempted by those who have no previous experience in lens maintenance. Most probably who repaired the lens before made a lousy job in servicing the focusing system.

This is the stop screw I refered to:


The image above (time 7:32) was extracted from this vídeo, which shows how to completely disassembly the CZJ Flektogon 35mm F2.4:

https://www.youtube.com/watch?v=oGJpmTslWfQ

NOTE: If you need to service only the focusing system, jump directly from 0:40 to 6:43 since it is neither necessary nor recommended to remove the optics and the aperture mechanism to get to the focusing sytem.


PostPosted: Thu Aug 06, 2020 8:45 pm    Post subject: Reply with quote

Gerald wrote:
Yes, I meant one full turn (360 degree), but I am afraid you'll have to disassembly the focusing system, what isn't too difficult to do, but but it is a task that shouldn't be attempted by those who have no previous experience in lens maintenance. Most probably who repaired the lens before made a lousy job in servicing the focusing system.

This is the stop screw I refered to:

NOTE: If you need to service only the focusing system, jump directly from 0:40 to 6:43 since it is neither necessary nor recommended to remove the optics and the aperture mechanism to get to the focusing sytem.


I've watched that video already, to be fair I searched and watched every video or picture about disassemble of Flektogon I could find on internet. But what about this video and this method?

https://www.youtube.com/watch?v=a-2jKyVezUc

Watch from 21:11, it's in Russian language (I speak Russian also), and the guy has trouble with focus not moving past 0,5 - 0,7 mark. He adjusts the lens in a different way and by his words the lens is assembled correctly and this adjusting is kinda what you are supposed to do after the assemble.

P.S.: that Flektogon in his video was almost dead and he made the best he could out of it. Good material for repairing.


PostPosted: Thu Aug 06, 2020 9:24 pm    Post subject: Reply with quote

aibo77 wrote:
But what about this video and this method?

This looks more reasonable than tearing the whole lens apart. Worth trying IMO.


PostPosted: Fri Aug 07, 2020 12:51 am    Post subject: Reply with quote

aibo77 wrote:


But what about this video and this method?

https://www.youtube.com/watch?v=a-2jKyVezUc

Watch from 21:11, it's in Russian language (I speak Russian also), and the guy has trouble with focus not moving past 0,5 - 0,7 mark. He adjusts the lens in a different way and by his words the lens is assembled correctly and this adjusting is kinda what you are supposed to do after the assemble.



The procedure described in the video is an adjustment to set the focus to infinity for a lens which was correctly assembled. That adjustment compensates for the inevitable optical and mechanical variations from lens to lens during manufacturing. It is not a workaround to circunvent an incorrect lens assembly. If the focus ring does not reach the infinity mark, it is a sure indication that the focusing mechanism has been incorrectly assembled.


PostPosted: Fri Aug 07, 2020 4:39 am    Post subject: Reply with quote

aibo77 wrote:
Alex TG wrote:
First you should sheck if just the focusing ring is misaligned or the whole lens.
Does it focus to infinity when fully retracted and to 0.2m when fully expanded? If yes, then it's just the focusing ring.


Yes it focuses through the whole range, it's just the markings that don't align to the red stripe, too much space in front of 0.2 mark and doesn't go till infinity mark.

So you're saying that when the focus ring hits the infinity stop that the image is sharp but the alignment of the scale is off, then there is nothing wrong with the helicoid, the issue is the focus ring or the DOF scale are not aligned properly.


PostPosted: Fri Aug 07, 2020 8:26 am    Post subject: Reply with quote

Lightshow wrote:
aibo77 wrote:
Alex TG wrote:
First you should sheck if just the focusing ring is misaligned or the whole lens.
Does it focus to infinity when fully retracted and to 0.2m when fully expanded? If yes, then it's just the focusing ring.


Yes it focuses through the whole range, it's just the markings that don't align to the red stripe, too much space in front of 0.2 mark and doesn't go till infinity mark.

So you're saying that when the focus ring hits the infinity stop that the image is sharp but the alignment of the scale is off, then there is nothing wrong with the helicoid, the issue is the focus ring or the DOF scale are not aligned properly.


I'm saying that when I turn the focusing ring to infinity, the red stripe doesn't hit the infinity mark, but the lens is focused to infinity. So it's all good with the lens, the moving part fully contracts and retracts in it's helicoid, it just doesn't properly correspond to the distance scale markings. So that can be adjusted by loosening the focus stop screw and adjusting the ring to match the scale?


PostPosted: Fri Aug 07, 2020 1:07 pm    Post subject: Reply with quote

aibo77 wrote:

I'm saying that when I turn the focusing ring to infinity, the red stripe doesn't hit the infinity mark, but the lens is focused to infinity. So it's all good with the lens, the moving part fully contracts and retracts in it's helicoid, it just doesn't properly correspond to the distance scale markings. So that can be adjusted by loosening the focus stop screw and adjusting the ring to match the scale?


The stop screw is just a... stop! There is nothing to "adjust" there. If the focusing ring doesn't reach infinity, it is because something is preventing it. This usually happens when the fine-threaded helicoid is one turn off. My suggestion is to buy a cheap Pentacon 50mm F1.8 lens and take it apart to learn how the focusing mechanisms of the lenses made in former East Germany work.


PostPosted: Fri Aug 07, 2020 3:57 pm    Post subject: Reply with quote

[quote="Gerald"]
aibo77 wrote:


The procedure described in the video is an adjustment to set the focus to infinity for a lens which was correctly assembled. That adjustment compensates for the inevitable optical and mechanical variations from lens to lens during manufacturing. It is not a workaround to circunvent an incorrect lens assembly. If the focus ring does not reach the infinity mark, it is a sure indication that the focusing mechanism has been incorrectly assembled.


But in that video, the focusing couldn't reach the infinity mark on the distance scale as mine does. It was stoping near the 0.7 mark (while mine stops about 10m mark). The person adjusted the lens and it started reaching the infinity mark. So isn't it the right way to adjust the lens after assembling?


PostPosted: Fri Aug 07, 2020 7:42 pm    Post subject: Reply with quote

[quote="aibo77"]
Gerald wrote:
aibo77 wrote:


The procedure described in the video is an adjustment to set the focus to infinity for a lens which was correctly assembled. That adjustment compensates for the inevitable optical and mechanical variations from lens to lens during manufacturing. It is not a workaround to circunvent an incorrect lens assembly. If the focus ring does not reach the infinity mark, it is a sure indication that the focusing mechanism has been incorrectly assembled.


But in that video, the focusing couldn't reach the infinity mark on the distance scale as mine does. It was stoping near the 0.7 mark (while mine stops about 10m mark). The person adjusted the lens and it started reaching the infinity mark. So isn't it the right way to adjust the lens after assembling?

rewatch the video, in the beginning it shows the focus ring at the infinity mark, I believe the video was only for cleaning the aperture system and relubing the helicoid(with fingers? Eeech, what a clumsy way to apply grease, buy a $2 artist brush to apply grease), I didn't see any adjustments being done, I'd have to have the lens in front of me to figure out where the misalignment is coming from, .


PostPosted: Fri Aug 07, 2020 10:23 pm    Post subject: Reply with quote

Lightshow wrote:

rewatch the video, in the beginning it shows the focus ring at the infinity mark, I believe the video was only for cleaning the aperture system and relubing the helicoid(with fingers? Eeech, what a clumsy way to apply grease, buy a $2 artist brush to apply grease), I didn't see any adjustments being done, I'd have to have the lens in front of me to figure out where the misalignment is coming from, .




This is where he starts from. Focusing ring turns only til 0,5 - 0,7 distance mark. The lens is beaten up and has the red stripe mark scratched off. I can also hear and understand what he is saying, so he confirms that the focusing ring turns only til "0,5 - 0,7" mark and doesn't go till "infinity" mark.


PostPosted: Sat Aug 08, 2020 3:52 pm    Post subject: Reply with quote

If the lens is correctly focused at infinity but does not travel the whole distance of the focus ring, such that infinity comes at eg. 10m gradation, then something is either obstructing it or the focus ring/distance scale has been fastened at the wrong position. The focus ring can freely rotate to any position on some lenses regardless of where the short/fine helicoid (for achieving image infinity) sits.
Unfortunately I don't have this lens so I can't check but I have a feeling you only need to reset the position of the focusing ring and then screw it down to the fine thread, without the fine thread shifting from its correct position.
Watch for about 30s from here to see what I mean: https://youtu.be/7ZGUTskxz5k?t=1621

If the focus ring does not freely rotate on this lens and secure with cone/grub screws like above, then you will have to play with the fine and coarse focus helicals to find the correct position, because it means the small thread is too tight and the whole lens and aperture unit is 'bottoming out' to the rear lens section/mount as the front section sinks towards infinity.